The present invention relates generally to a method and apparatus for repairing a workpiece, such as turbine components and the like.
As used herein, the term “turbine components” is intended to include individual turbine blades, blades mounted on a disk, blades that are machined integral to a rotor or to an impeller (e.g. Blisks), air foils, vanes and shrouds.
During use, the material at the outer tips, edges or surfaces of turbine components is worn away and damaged, and, in addition, these turbine components tend to become distorted, twisted and bent during use, caused in part by the high temperatures and the temperature variations to which the turbine components are exposed. It is well known that these turbine components can be repaired by welding new materials at the tips, edges or surfaces of the turbine components to replace the material that has been worn away and/or damaged during use by using, for example, a laser powder fusion welding system.
However, because of the aforesaid distortion of the turbine components, the turbine components themselves become twisted and bent, and the uniformity of the turbine components in their original condition is lost. Moreover, because each turbine component is exposed to different operating conditions, the distortion of the turbine components from one turbine component to the next can be significantly different from one another. Accordingly, because of these distortions, and the variations in the distortions, it is difficult to repair turbine components by welding new material at the outer tips, edges or surfaces of the turbine components.
When a distorted turbine component is repaired, any coatings that may be normally applied to the turbine component are removed, and then the turbine component is machined to remove any damaged portions of the turbine component tips, edges or surfaces. Then, conventional welding equipment is used to restore the lost material at the tips, edges or surfaces of the turbine component, and additional steps may be taken to complete the repair process as is well known in the art.
Perhaps the most common welding method for repairing a distorted turbine component, such as a turbine blade, is a manual operation in which a workman manually follows the distorted configuration of the turbine blade by simply holding the welding equipment at a proper location as the welder moves the welding equipment along the outer edge of the distorted turbine blade. The manual operation can be done using MIG, TIG Welding, or plasma arc heat sources. This manual operation is obviously a slow and labor-intensive operation, and in many cases the quality of the weld is poor, and in some cases must be reworked completely.
Additionally, some automated welding systems are used which rely on external measuring methods to probe or digitize a part to determine its configuration, and transfer digital information to a separate welding machine which performs the welding. However, these systems are cumbersome to change part-holding fixtures from one machine to another to retained referenced datum, and they are quite slow in most cases. Accurate data can be lost or changed in translation.
Also, some machines use a system by which video or photographic two-dimensional images are taken within the machine to reverse engineer the turbine component, but these machines are limited to obtaining two-dimensional images at different views, and multiple 2D views can not faithfully reverse engineer some turbine component surfaces which are obviously three-dimensional. These machines generally use either laser powder fusion or plasma methods. Typical illustrations of a machine of this type are disclosed in U.S. Pat. No. 4,998,005 and U.S. Published Patent Application No. 2006/0067830.